It is now commonly accepted that the vision impairing disease known as cataracts can be alleviated by surgically replacing the natural lens of the eye with an artificial intraocular lens. The condition of cataracts is characterized by a clouding or opacification of the natural lens of the eye so that the amount of light which reaches the retina is substantially reduced or completely eliminated.
The anatomy of the eye 1 is shown schematically in FIG. 1. The cornea 2 forms the front surface of the eye and connects with the ciliary muscle 3, from which the iris 4 extends. Iris 4 divides the front portion of the eye into the anterior chamber 5, between iris 4 and cornea 2, and a posterior chamber 6 behind the iris 4. The capsular bag 7 in which the natural lens of the eye is encased is supported from ciliary muscle 3 by suspensory ligaments 8, called zonules. Pupil 9 is the aperture at the center of iris 4 through which light passes to the posterior chamber 6 and to the back of the eye.
During cataract surgery, a portion of the anterior surface of capsular bag 7 is removed by well-known techniques leaving an anterior flap 10 at the anterior edges of capsular bag 7. The cataract lens (not shown) is then removed and the interior of the remaining capsular bag 7 is cleaned and polished by similarly well-known surgical techniques. The eye is now ready to receive an intraocular lens implant.
A variety of lenses are available for implantation into the eye. Some lenses have been designed for placement in anterior chamber 5. Other lenses have been specifically designed for placement in posterior chamber 6 and particularly in capsular bag 7 in posterior chamber 6. This patent application is directed to a medical instrument for facilitating the insertion of an intraocular lens into capsular bag 7 in the posterior chamber 6 of eye 1 behind iris 4. Thus, this application will focus on describing the use of the instrument for inserting a posterior chamber lens into the capsular bag. However, because of the ease of releasing the superior haptic of the lens with the instrument it is also believed to facilitate insertion into the anterior chamber of the eye.
Posterior chamber intraocular lenses 20 generally have two principal parts: a medial, light-focusing body 21 (also called the optic) made of a nontoxic, plastic material which will replace the natural lens of the eye and focus light on the retina; and, haptic support portions 22 and 24 which extend from optic 21 to the anatomy of the eye and provide a means for fixing and holding optic 21 in its proper position within the eye. Haptic support loops 22 and 24 are commonly made of a very flexible, resilient, filamentary plastic material like polypropylene.
In many instances, it is highly desirable to place the intraocular lens implant in capsular bag 7 in the same general position that the natural lens of the eye resided before removal.
As shown particularly in FIG. 1, the intraocular lens implant 20 is inserted through an incision 12 made in the base of cornea 2. The patient is usually lying on his back with the doctor standing facing the top of the patient's head. Incision 12 may be made at a position called the superior part of the eye. The intraocular lens is inserted from the superior portion of the eye toward the inferior portion of the eye. The first haptic to be inserted into the eye is called the inferior haptic. The second haptic to be inserted into the eye is called the superior haptic. This terminology of inferior position and superior position is generally used in the industry, and inferior positions are those spaced further away from the entrance incision, and superior positions are those spaced closer to the entrance incision.
The first haptic support 22, also called the inferior haptic, is inserted directly into the capsular bag 7. As the inferior haptic 22 is inserted into the eye, it can be easily slanted through pupil 9, and proper placement of the inferior loop in capsular bag 7 is relatively easy to achieve for the skilled surgeon. On the other hand, the other haptic support loop 24 (also known as the superior loop) can be difficult to insert in capsular bag 7.
A variety of existing tools are used to facilitate the insertion of the superior loop 24 in capsular bag 7. A tool with a small hook on the end can be used to push superior loop 24 in the direction of inferior loop 22. The natural resilience of the haptic loops 22 and 24 tend to hold superior loop 24 in the insertion hook. However, as the surgeon attempts to release superior loop 24 from the insertion hook, the natural resilience of superior loop 24 causes it to continue to engage the hook making it difficult for the surgeon to release superior loop 24 and still completely control its motion to assure placement of superior haptic 24 in capsular bag 7. Sometimes superior loop 24 will end up in the groove 14 between the posterior surface of iris 4 and ciliary muscle 3.
Many surgeons find that an angular rotation of the wrist or fingers is required to release the frictional engagement between superior haptic 24 and the tool, so that superior haptic 24 may slide off the tool into capsular bag 7. Such angular movement of the surgeon's wrist may cause either the intraocular lens 20 or the tool itself to touch portions of the interior anatomy of the eye. Touching the interior surface of cornea 2 is particularly undesirable because it is very delicate and easily damaged.
There are other difficulties associated with the use of such hooks. As the user grasps superior haptic 24 with the hook and urges it inferiorly, optic 21 tends to rotate and haptic 24 deflects laterally, both of which tend to cause haptic 24 to slide off such a hook. This makes it more difficult to maneuver superior haptic 24 to its desired portion. Similar difficulties are experienced when inserting an anterior chamber lens.
It would be desirable to have a surgical instrument which would facilitate the insertion of superior loop 24 into capsular bag 7 while minimizing the movement of the tool. It can be difficult to place superior haptic 24 in capsular bag 7, because capsular bag 7 is hard to reach and it cannot be easily visualized by the surgeon. Thus, even though superior haptic 24 may appear to be placed in the superior side of the capsular bag 7, it is very difficult to confirm that this is actually the case.
It would be desirable to have an insertion tool that would easily, quickly and reliability permit the surgeon to assure that he has placed superior haptic 24 of the lens 20 in capsular bag 7.